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Multimedia Messaging Service (MMS) is a standard way to send messages that include multimedia content to and from mobile phones. It extends the core SMS (Short Message Service) capability that allowed exchange of text messages only up to 160 characters in length.
The most popular use is to send photographs from camera-equipped handsets, although it is also popular as a method of delivering news and entertainment content including videos, pictures, text pages and ringtones.
Multimedia messaging services were first developed as a captive technology that would enable service providers to "collect a fee every time anyone snaps a photo."
Early MMS deployments were plagued by technical issues and frequent consumer disappointments, such as having sent an MMS message, receiving a confirmation it had been sent, being billed for the MMS message, to find that it had not been delivered to the intended recipient. Pictures would often arrive in the wrong formats, and other media elements might be removed such as a video clip arriving without its sound.
At the MMS World Congress in 2004 in Vienna, all European mobile operator representatives who had launched MMS, admitted their MMS services were not making money for their networks. Also on all networks at the time, the most common uses were various adult oriented services that had been deployed using MMS.
China was one of the early markets to make MMS a major commercial success partly as the penetration rate of personal computers was modest but MMS-capable cameraphones spread rapidly. The chairman and CEO of China Mobile said at the GSM Association Mobile Asia Congress in 2009 that MMS in China is now a mature service on par with SMS text messaging.
Europe's most advanced MMS market has been Norway and in 2008 the Norwegian MMS usage level had passed 84% of all mobile phone subscribers. Norwegian mobile subscribers average one MMS sent per week.
MMS messages are delivered in a completely different way from SMS. The first step is for the sending device to encode the multimedia content in a fashion similar to sending a MIME e-mail (MIME content formats are defined in the MMS Message Encapsulation specification). The message is then forwarded to the carrier's MMS store and forward server, known as the MMSC (Multimedia Messaging Service Centre). If the receiver is on another carrier, the relay forwards the message to the recipient's carrier using the Internet.
Once the MMSC has received a message, it first determines whether the receiver's handset is "MMS capable", that it supports the standards for receiving MMS. If so, the content is extracted and sent to a temporary storage server with an HTTP front-end. An SMS "control message" containing the URL of the content is then sent to the recipient's handset to trigger the receiver's WAP browser to open and receive the content from the embedded URL. Several other messages are exchanged to indicate status of the delivery attempt. Before delivering content, some MMSCs also include a conversion service that will attempt to modify the multimedia content into a format suitable for the receiver. This is known as "content adaptation".
If the receiver's handset is not MMS capable, the message is usually delivered to a web based service from where the content can be viewed from a normal internet browser. The URL for the content is usually sent to the receiver's phone in a normal text message. This behaviour is usually known as the "legacy experience" since content can still be received by a phone number, even if the phone itself does not support MMS.
The method for determining whether a handset is MMS capable is not specified by the standards. A database is usually maintained by the operator, and in it each mobile phone number is marked as being associated with a legacy handset or not. This method is unreliable, however, because customers can change their handset at will, and many of these databases are not updated dynamically.
MMS does not utilize one's own operator maintained data plan to distribute multimedia content. Operator maintained data plans are only used when message included links (if any) are explicitly clicked.
E-mail and web-based gateways to the MMS (and SMS) system are common. On the reception side, the content servers can typically receive service requests both from WAP and normal HTTP browsers, so delivery via the web is simple. For sending from external sources to handsets, most carriers allow MIME encoded message to be sent to the receiver's phone number with a special domain. An example of this would be PTN@messaging.carrier.com, where PTN is the public telephone number. Typically the special domain name is carrier specific.
There are some interesting challenges with MMS that do not exist with SMS:
Although the standard does not specify a maximum size for a message, 300 kB is the current recommended size used by networks due to some limitations on the WAP gateway side.